1. Field of the Invention.
The present invention relates generally to devices and machines used in composting and recycling operations, but more particularly to machines used to grind solid waste into reusable, treatable, or readily degradable forms.
Modern management of discarded materials began in the late 1800's. By the 1890's more than half of America's cities utilized some system of collection and disposal of refuse. The three early categories of refuse were ashes, food and dry rubbish. Each of the three categories had a specific secondary use making what can be referred to as modern day landfills, unnecessary. Food scraps were fed to animals on the farms, the ashes filled potholes in roads and "unhealthy" swamps, and the dry rubbish was sorted for valuables. Rags, paper and the like, made more paper, and metals went back into production as reusable goods or sold.
By the 1930's food scraps, rags and paper were mixed together and canned to an incinerator. Incineration was cheaper and easier because the mixture of materials could be collected at one time and burned together. Incineration, however, introduced harmful byproducts and pollutants into the atmosphere.
In the 1940's, sanitary landfills proliferated. By the 1950's, with the explosion of consumer products focusing on disposability, the amount of refuse generated increased dramatically. In fact, some reports suggest that by the 1970's 5 pounds of garbage per capita were discarded daily as compared to 2.7 pounds in the 1920's. In the 1980's, the public began to appreciate that congested landfills were polluting drinking water. At this time, recycling began its resurgence. Today, what was once something associated with dedicated gardeners or environmental activists, is at the forefront of community living.
Recycling and composting is now being recognized as an efficient way to handle organic solid waste and to reintroduce nutrients into the nutrient depleted soil of the earth. In addition, recycling has transformed discarded materials, such as cellulose, wood, grass, leaves, cardboard, pallets, tree limbs, etc., plastics (polystyrene, polyethylene, polypropylene, PVC, etc.), glass, and ceramics into reusable materials.
2. Description of the Related Art
Hammer mills, grinders, and shredders are three types of machines found in the art to which the invention relates. All three may be used to create compost from organic materials and convert inorganic materials into a reusable or particle form.
Hammer mills incorporate a rotating drum or spindle with free-floating hammers. The hammer mill is designed to spin at a relatively high speed. Material placed in front of the rotating drum is impacted by the hammers. Hammer mills, therefore, do not cut, shred or tear the material, but rely on impact forces to, pulverize the material.
Shredders typically incorporate a pair of rotatable parallel shafts having spaced apart cutters. The cutters resemble flats formed on circular lobes. A first shaft is positioned in parallel alignment with a second shaft enabling the lobes of the first shaft to occupy the interstices between the lobes of the second shaft and vice versa.
The shafts are designed to rotate toward one another. The cutters (flats) pull the material to be shredded downward between the shafts. The pulling action by the cutters shreds the material. In an overload condition, the shafts are designed to reverse direction momentarily before resuming the shredding rotations.
Grinders of the related art incorporate a rotating disk or drum. The drums generally have a flat abrasive surface or have cutters formed integral therewith. To grind material with the related art grinders, the user activates the, rotating drum or disk causing it to spin at high speed. The user then introduces the workpiece into the grinder to contact the rotating drum or disk. The rotating drum cuts, tears, and shreds the workpiece. The hammer mill and shredder are not particularly useful for recycling a variety of materials. That is, each device has its own inherent limitations such that certain materials are processed much more easily than others.
Until now, it is believed that a grinding apparatus for efficiently recycling and converting solid material such as cellulose, plastics, combination materials, glass, ceramics, and other materials into a manageable useful product, such as a fine grade of granule or readily degradable humus, has not been invented.